1. Field of the Invention
The invention relates to a level indicator for indicating the decibels the ratio between the instantaneous value and an extreme value of a sample of an analog signal, which values are given by binary coded digital signals of a fixed number of bits, which level indicator comprises a digital signal converting circuit, which for each digital signal supplies a drive signal to a read-out device equipped with a display device.
Such a level indicator for indicating the magnitude of a digital signal may be employed, for example, for adjusting the recording level in a digital audio recorder and in digital mastering equipment for producing compact digital discs.
2. Description of the Related Art
Such a level indicator is known from U.S. Pat. No. 3,952,247. In this indicator the samples of the analog signal are applied to a parallel analog-to-digital converter, which converts the analog signal into a parallel digital signal. This parallel signal is applied to a decoding device, whose outputs are connected to driver circuits for display elements constituted by light-emitting diodes. The ratio between the instantaneous value and the maximum value of the signal in decibels can be read from a scale adjacent these diodes. For each value of the digital signal the decoding device generates a signal on an appropriate output, which signal is further processed by the driver circuits to drive a column of display elements corresponding to the magnitude of the relevant digital signal. The driver circuits comprise facilities which prolong the display time for brief peaks in signal strength, so that these peaks are more easily discernible.
A disadvantage of this known level indicator is that the decoding device must decode a large number of levels to obtain a large display range with a high resolution, which in combination with the associated driver circuits renders the indicator rather complex with a large number of components. Another drawback is that the known level indicator does not provide a decibel-linear readout over the entire range.